How to escape a sinking car
DON'T PANIC!
If the car is still sinking, or if it is still afloat, then it is crucial to escape as fast as possible before you sink deeper and put yourself in more danger. On the other hand, if the car has hit the floor already, you'll probably have a few minutes before the car fills up on its own through the ventilators and other holes, and one carful of air is enough to sustain you for at least that long. You will therefore probably have time to settle everyone down and explain the plan to your passengers. Points with an asterisk (*) below are those you should only do if you have time.
The Plan
DO NOT attempt to open your car door. If the car is fully submerged, then the water pressure from the outside will make the door many times heavier than normal: if you're more than ten metres underwater, the door will be like a tonne weight. This is the principle that submarine airlock hatches work on: they all open outwards, and water pressure outside forces them shut while the submarine is submerged. Instead, you need to equalise the pressure between the inside and the outside of the car. Basically, you have to fill the car with water by winding down the windows. Once this is done, the doors will open with great ease and you can escape.
What to do
*Make those people who aren't so good at holding their breath change seats so that they're seated as close to the door as possible. This gives them a better chance of escaping.
*Got any warm clothing? Put it all on, grab hold of the stuff you can't. If you crashed anywhere other than the Carribean or Mediterranean Seas, then regardless of how quickly you escape, and regardless of whether or not you make it to land soon afterwards, when you get in the water it will probably be cold. You may even have hypothermia to contend with if it happens to be winter. So wrap up.
*Exceptions to the warm clothing rule: boots, jeans. Boots are heavy and will weigh you down. Jeans soak up water and also weigh you down. If you have these on, and you are uncertain about swimming while wearing them, then take them off.
If you've crashed into, for example, the River Thames, then the water is also likely to be very dirty. There is nothing you can do about this, except to try to keep your eyes and mouth closed for as long as possible while you are underwater.
MAKE SURE ALL THE DOORS ARE UNLOCKED. Otherwise you might as well be signing your own death warrant. If there are child locks on any of the doors, tell the people who're going to use those doors. If possible, move them to a door which doesn't have a child-lock. Otherwise, they will have to swim through the window when the time comes.
*Make sure that everybody's escape is arranged for and that everyone knows exactly how they are getting out. Nobody wants to be left behind.
If there is a dog in the back, LEAVE IT. YOUR life and those of your passengers are more important than any dog. *I mean, fine, take down the wire mesh guard that's keeping it trapped in the back, but seriously, get your priorities straight.
Take a few deep breaths, then finally take a deep breath and hold it. Close your eyes. Prepare to get wet.
As quickly as you possibly can, open your windows as far as they can go. This is to allow the car to fill up with water as quickly as possible.
Once the windows are open by a small amount, a lot of water will rush in and soak you. Disregarding this, you have to keep opening the window until it won't go any further.
Wait until the rushing of water stops.
NOW open the car doors and swim out. If there is a large enough sunroof which can be slid fully open (as opposed to merely jutting upwards by a few degrees) then this is a viable means of escape as well. If there are kids, send them first, or grab hold of them as you go.
If you are more than ten metres down, remember to exhale all the way up. The air in your lungs will expand as you rise, and it is stupid and dangerous to attempt to hold it all in. If you are a seriously long way down, see also The Bends.
Oh, and forget about recovering your car.
